A system configured to calculate a route from, for example, a present location of a vehicle to a destination provides a route guidance by calculating a route using route calculation data and displaying the calculated route superimposed on a map screen. In a case where a present location of the vehicle deviates from the calculated route, the system recalculates the route and notifies a user (driver) that the route is recalculated by outputting a voice notification message, for example, “You are deviating from the scheduled route. New route is being recalculated.” A present location of the vehicle deviates from the calculated route in a case where the user deviates from the route accidentally by mistake or in a case where the user deviates from the route purposefully. In the former case, the user is probably a stranger in a present area and has no idea about the present location of the vehicle. It is therefore desirable to output a voice notification message to eliminate anxiety of the user. On the contrary, in the latter case, the user is probably familiar with the area and knows the present location of the vehicle. Hence, the user may possibly be annoyed by an output of a voice notification message.
Such being the case, Patent Literature 1 describes a technique of determining whether the user deviates from the route accidentally by mistake or purposefully according to user's preference.